1. Field of the Invention
This invention relates to a door lock, particularly to one able to prevent from being locked by an unexpected exterior force.
2. Description of the Prior Art
As shown in FIG. 1, a conventional door lock mainly includes a shell 10, a dragging mechanism 11 set inside the shell 10, a sleeve 13 extended axially from the shell 10, a set of driving tubes 14 in the sleeve 13 and a fixing member 15 set outside the sleeve 13.
The fixing member 15 is used to keep a door lock fixed on a door. Each driving tube 14 is connected with a L-shaped handle 16 at one end, which is able to drive the driving tube 14 to spin against the sleeve 13 axially while the handle 16 is turned, so that the dragging mechanism 11 in the shell 10 is drawn back. One of the driving tubes 14 is fixed with a button 17 provided with an extending body 170 at one end and provided with a sliding groove 140 at an outer annular rim. The sliding groove 140 communicated with an insert groove 141 at its one end can let the button 17 move along it axially. When the button 17 is pressed down, the extending body 170 is to slide along the sliding groove 140 to enter the insert groove 141, keeping the button 17 locked, unable to open the door lock.
But, the extending body 170 of the button 17 in the conventional door lock is very easy to be guided into the locking groove 141 by an unexpected exterior force. Therefore, when a door is opened, the button 17 sometime is casually pressed by an exterior force, such as an impact of the door against a wall, to make it locked. If such a door with the lock kept in the locked condition is pushed or pulled to close unintendedly, a person may be locked outside the door, unable to open it.